Enzymes Lesson

Enzymes

Chemical Reactions

⚫ In order for chemical reactions to take place, enzymes must

be present to help speed up the reaction.

⚫ Chemical bonds connect atoms

to make molecules.

⚫ Chemical reactions can do two things:

⚪ They can join atoms to make molecules.

⚪ They can break bonds in molecules.

⚫ The sum of all the chemical reactions that take place within a

cell is referred to as the cell’s metabolism.

Chemical Reactions

⚫ The molecules or atoms at the beginning of a

chemical reaction are called the reactants.

⚫ The materials produced by the chemical

reaction are called products.

2H2 + O2 🡪 2H2O

Reactants

Product

Law of Conservation of Matter/Energy

⚫ Matter and Energy cannot be created or destroyed in

chemical reactions

Energy-Absorbing vs. Energy-Releasing Reactions

Energy-Absorbing Reaction
Endothermic Reaction

Energy-Releasing Reaction

Endothermic

Exothermic

Multiple Choice

The molecules or atoms at the beginning of a chemical reactions are called ______.

• Enzymes

• Reactants

• Products

• Active Sites

Multiple Choice

Chemical reactions in which the products have more energy than the reactants are called _________ reactions.

• Energy Releasing

• Energy Absorbing

• Endergonic

• Exergonic

Multiple Choice

Which graph shows an exergonic reaction (energy releasing)?

• On the left.

• On the right.

Chemical Energy and ATP

⚫ ATP

⚪ Adenosine triphosphate

⚪ Compound that cells use to store

and release energy

⚪ Made of adenine, 5-carbon sugar

(ribose), and 3 phosphate groups

⚫ ADP

⚪ Adenosine diphosphate

⚪ Made of adenine, 5-carbon sugar

(ribose), and

2 phosphate groups

Chemical Energy and ATP

Chemical Energy and ATP

⚫ Why is ATP useful to

cells?

⚪ It can easily release

energy and store energy
by breaking and forming
bonds between its
phosphate groups

Chemical Energy and ATP

⚫ Different ways cells use ATP

⚫ Cell transport (sodium/potassium

pumps)

⚫ Protein synthesis

⚫ Produce light (fireflies)

⚫ Contract muscle

⚫ Movement (cilia and flagella)

⚫Why do cells only have a small amount of ATP?

⚫ Not good for storing LARGE
amounts of energy

*Regenerate ATP from ADP as needed

*Glucose have 90 times more energy

Introduction to Enzymes

⚫ Enzymes are proteins that act as biological

catalysts.

⚪ Catalysts - speedup chemical reactions.

⚪ Enzymes- speedup chemical reactions in living things.

Enzymes are PROTEINS

⚫ The building blocks of proteins are called amino acids.

⚫ Chains of amino acids are joined together and folded to give

each protein a specific shape.

⚪ Different order of amino acids = different protein (different

shape)

⚫ A protein’s function (job) depends on its shape.

⚫ Proteins will stop working if their shape is damaged.

Structure and Function of Enzymes

⚫ A substrate is the molecule that the

enzyme changes.

⚪ It is the reactant a chemical reaction controlled by an

enzyme!

⚫ Each enzyme has an active site which

is the place where the enzyme and
substrate attach.

Structure and Function of Enzymes

⚫ During a chemical reaction, the enzyme helps the

reactant turn into product, however, the enzyme is not
changed.

⚫ Enzymes can be used over and over again.

Reactant/Substrate🡨
🡨Product

Enzyme🡪
No change in the
shape of
enzyme/ready to
catalyze next
reaction. 


The molecule on which an enzyme acts:

A.

Catalyst

B.

Substrate

C.

Metabolism

D.

Homeostasis

Multiple Choice

Enzymes are specific types of which biological
macromolecule?

• nucleic acids
• lipids
• proteins
• carbohydrates

Multiple Choice

Which shape is an enzyme?

• A

• B

• C

• D

Multiple Choice

Which shape is the product of the reaction?

• A

• B

• C

• D

Enzyme Specificity

⚫ Enzymes are very specific. This means that each

enzyme can only work on one substrate.

⚪ For example:

� 1. Maltase only breaks down maltose (a carbohydrate).

� 2. Lipase only works on certain lipids.

� 3. Protease only works on certain proteins.

⚫ Does a specific enzyme work on more than one

substrate?

• NO!!!

Enzyme Specificity

⚫ Therefore you need thousands of different

enzymes for the thousands of different
chemical reactions in your body.

⚫ The names of many enzymes (Amylase, Lipase,

Pepsin, Trypsin) usually end in ase or in.

Enzyme Specificity

⚫ The diagram below shows the lock and key modelof how

enzymes work on a specific substrate.

⚫ Just like every lock has one type of key that opens it, every

substrate has one type of enzyme that works on it.

How Enzymes Work

⚫ Lower activation energy

⚪ Energy that is needed to start a chemical reaction

⚪ Puts substrates in a good position to make/break bonds with

each other

Reaction with enzyme vs. Reaction without enzyme

The energy that is required to start a chemical

reaction is called

A.
Endothermic
energy

B.
Exothermic energy

C.
Enzyme energy

D.
Activation energy

Multiple Choice

What is the energy that is required to start a chemical called?

• kinetic energy
• thermal energy
• activation energy
• potential energy

Multiple Choice

How do catalysts speed up or facilitate chemical reactions? 

• By slowing down the reaction rate
• By lowering the activation energy
• By increasing the activation energy
• By changing the equilibrium constant

Enzymes lower activation energy

Enzymes and Their Environment

⚫ Most cells function best within a narrow range

of temperature and pH.

⚫ At very low temperatures, enzymes work too

slow.

Enzymes and Their Environment

⚫ At high temperatures or extremes of pH

the enzymes lose their shape.

⚪ What would happen if a key lost its shape?

� It wouldn’t turn or fit in the hole.

⚪ What will happen if an enzyme lost its

shape?

� It wouldn’t recognize or bind with it’s

substrate.

Enzymes and Their Environment

⚫ When an enzyme loses its shape and can no

longer work correctly, it has been denatured.

Multiple Choice

Enzymes stop functioning if:

• They are denatured or if the conditions for their activity are not optimal.
• They are destroyed by heat or chemicals.
• They are unable to bind to their substrate.
• They are inhibited by other molecules.

Multiple Choice

When proteins, such as enzymes, lose their specific shape they have become __________.

• unfolded
• disrupted
• denatured
• misshapen

What is the optimum pH for the enzyme pepsin?

A.
1

B.
2.5

C.
5

D.
6.5

pepsin
trypsin

Multiple Choice

What is the optimum pH for the enzyme pepsin?

• 1

• 2.5

• 6

• 6.5

Introduction to Macromolecules

Building Macromolecules

⚫ Polymer – large biomolecules made by linking together a

large number of the same type of subunit

⚫ Monomer- small molecule that is a subunit of a polymer

(building blocks)

⚫ Chemical reactions link monomers together to build

polymers or break down polymers into monomers

⚪ Enzymes help speed up these reactions!!

Organic Macromolecules (Polymers)

MONOMER

POLYMER

Amino Acid

Protein

Sugar

(monosaccharide)

Carbohydrate

(polysaccharide)

Nucleotide

Nucleic Acid

Polymers are large biomolecules made of repeated

subunits called

A.
Enzymes

B.
Sugars

C.
Monomers

D.
Proteins

Proteins are polymers made of monomers called

A.
Monosaccharides

B.
Fatty acids

C.
Amino acids

D.
nucleotides